/**
 * WhatClr.c -- Display Color under Cursor
 *              (c) Charles Petzold, 1998
 */

#include <windows.h>

#define ID_TIMER 1

void FindWindowSize(int *, int *);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("WhatClr");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,
                        TEXT("What Color"),
                        WS_OVERLAPPEDWINDOW | WS_CAPTION | WS_SYSMENU | WS_BORDER,
                        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
                        NULL, NULL, hInstance, NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

void FindWindowSize(int *pcxWindow, int * pcyWindow) {
    HDC hdcScreen;
    TEXTMETRIC tm;
    hdcScreen = CreateIC(TEXT("Display"), NULL, NULL, NULL);
    GetTextMetrics(hdcScreen, &tm);
    DeleteDC(hdcScreen);

    *pcxWindow = 2 * GetSystemMetrics(SM_CXBORDER) + 12 * tm.tmAveCharWidth;
    *pcyWindow = 2 * GetSystemMetrics(SM_CYBORDER) + 
                GetSystemMetrics(SM_CYCAPTION) +
                2 * tm.tmHeight;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static COLORREF cr, crLast;
    static HDC hdcScreen;
    HDC hdc;
    PAINTSTRUCT ps;
    POINT pt;
    RECT rc;
    TCHAR szBuffer[16];

    switch (message)
    {
        case WM_CREATE: {
            hdcScreen = CreateDC(TEXT("DISPLAY"), NULL, NULL, NULL);
            
            SetTimer(hwnd, ID_TIMER, 100, NULL);
            return 0;
        }
        case WM_SIZE: {
            // cxClient = LOWORD(lParam);
            // cyClient = HIWORD(lParam);
            return 0;
        }        
        case WM_TIMER: {
            GetCursorPos(&pt);
            cr = GetPixel(hdcScreen, pt.x, pt.y);
            SetPixel(hdcScreen, pt.x, pt.y, 0);
            if (cr != crLast) {
                crLast = cr;
                InvalidateRect(hwnd, NULL, FALSE);
            }
            return 0;
        }
        case WM_PAINT: {
            hdc = BeginPaint(hwnd, &ps);
            
            GetClientRect(hwnd, &rc);
            wsprintf(szBuffer, TEXT("    %02X %02X %02X    "), GetRValue(cr), GetGValue(cr), GetBValue(cr));
            DrawText(hdc, szBuffer, -1, &rc, DT_SINGLELINE | DT_CENTER | DT_VCENTER);

            EndPaint(hwnd, &ps);
            return 0;
        }

        case WM_DESTROY: {
            DeleteDC(hdcScreen);
            KillTimer(hwnd, ID_TIMER);
            PostQuitMessage(0);
            return 0;
        }
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}